Hydrocarbon-soluble molybdenum catalyst precursors and methods for making same

ABSTRACT

Hydrocarbon-soluble molybdenum catalyst precursors include a plurality of molybdenum cations that are each bonded with a plurality of organic anions to form an oil soluble molybdenum salt. A portion of the molybdenum atoms are in the 3+ oxidation state such that the plurality of molybdenum atoms has an average oxidation state of less than 4+, e.g., less than about 3.8+, especially less than about 3.5+. The catalyst precursors can form a hydroprocessing molybdenum sulfide catalyst in heavy oil feedstocks. The oil soluble molybdenum salts are manufactured in the presence of a reducing agent, such as hydrogen gas, to obtain the molybdenum in the desired oxidation state. Preferably the reaction is performed with hydrogen or an organic reducing agent and at a temperature such that the molybdenum atoms are reduced to eliminate substantially all molybdenum oxide species.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention is in the field of upgrading heavy oil feedstocksinto lower boiling, higher quality materials. More particularly, theinvention relates to catalyst precursors containing molybdenum saltsthat can be mixed with heavy oil feedstocks to form, in situ, ahydroprocessing catalyst and a method for making the catalystprecursors.

2. Related Technology

World demand for refined fossil fuels is ever-increasing and willeventually outstrip the supply of high quality crude oil. As theshortage of high quality crude oil increases there will be an increasingdemand to find ways to better exploit lower quality feedstocks andextract fuel values from them.

Lower quality feedstocks are characterized as including relatively highquantities of hydrocarbons that have a boiling point of 524° C. (975°F.) or higher. They also contain relatively high concentrations ofsulfur, nitrogen and/or metals. High boiling fractions typically have ahigh molecular weight and/or low hydrogen/carbon ratio, an example ofwhich is a class of complex compounds collectively referred to as“asphaltenes”. Asphaltenes are difficult to process and commonly causefouling of conventional catalysts and hydroprocessing equipment.

Examples of lower quality feedstocks that contain relatively highconcentrations of asphaltenes, sulfur, nitrogen and metals include heavycrude and oil sands bitumen, as well as bottom of the barrel andresiduum left over from conventional refinery process (collectively“heavy oil”). The terms “bottom of the barrel” and “residuum” (or“resid”) typically refer to atmospheric tower bottoms, which have aboiling point of at least 343° C. (650° F.), or vacuum tower bottoms,which have a boiling point of at least 524° C. (975° F.). The terms“resid pitch” and “vacuum residue” are commonly used to refer tofractions that have a boiling point of 524° C. (975° F.) or greater.

Converting heavy oil into useful end products requires extensiveprocessing, including reducing the boiling point of the heavy oil,increasing the hydrogen-to-carbon ratio, and removing impurities such asmetals, sulfur, nitrogen and carbon forming compounds.

When used with heavy oil, existing commercial catalytic hydrocrackingprocesses become fouled or rapidly undergo catalyst deactivation. Theundesirable reactions and fouling involved in hydrocracking heavy oilgreatly increases the catalyst and maintenance costs of processing heavyoils, making current catalysts unsuitable for hydroprocessing heavy oil.

One promising technology for hydroprocessing heavy oils uses ahydrocarbon-soluble molybdenum salt that decomposes in the heavy oilduring hydroprocessing to form, in situ, a hydroprocessing catalyst,namely molybdenum sulfide. One such process is disclosed in U.S. Pat.No. 5,578,197 to Cyr et al., which is incorporated herein by reference.Once formed in situ, the molybdenum sulfide catalyst is highly effectiveat breaking up asphaltenes and other complicated hydrocarbons whilepreventing fouling and coking.

A significant problem with commercializing oil soluble molybdenumcatalysts is the cost of the catalyst. Even small improvements incatalyst performance can have a significant benefit to the cost of thehydrocracking process due to the increase in output and/or the reduceduse of the catalyst.

The performance of oil soluble molybdenum catalysts dependssignificantly on the concentration of the metal in the heavy oil and onhow well the catalyst precursor can be dispersed in the heavy oil.Improvements that can increase the percent of metal in the catalystprecursor while maintaining or improving solubility can improve theefficiency of hydrocracking heavy oils using oil soluble molybdenumcompounds.

SUMMARY OF THE INVENTION

The present invention relates to catalyst precursors having ahydrocarbon soluble molybdenum salt that can form in situ ahydrocracking catalyst for upgrading heavy oil feedstocks. The catalystprecursor includes a molybdenum salt comprising a plurality of cationicmolybdenum atoms and a plurality of organic anions. The organic anionspreferably have between 2 and 14 carbon atoms. In a preferredembodiment, at least a portion of the molybdenum atoms are bonded with 3organic anions and have an oxidation state of 3+ such that the pluralityof molybdenum atoms have an average oxidation state of less than 4+.

To obtain a catalyst precursor with at least a portion of the molybdenumatoms in a 3+ oxidation state, the catalyst precursor is made using astrong reducing agent. Suitable reducing agents include hydrogen and/ororganic reducing agents. The reducing agent reduces and stabilizes themolybdenum atoms during the reaction between the organic agent and themolybdenum atoms. Water is removed to make the reaction product solublein heavy oil.

In a preferred embodiment, the method of the present invention producesa catalyst precursor with an average oxidation state of less than 4+.The Mo³⁺ species present in the catalyst precursors enhance the in situformation of the MoS₂ catalyst. The Mo³⁺ atoms are less stable thanother forms of molybdenum, such as Mo⁴⁺, Mo⁵⁺, and Mo⁶⁺. Because Mo³⁺ isless stable, it more readily decomposes in heavy oil and forms thedesired catalytic molybdenum sulfide compounds. While the foregoingtheories are believed to contribute at least in part to the improvedperformance of the catalysts of the present invention, the invention isnot limited to these theories.

The use of a reducing agent can also be advantageous to preventformation of undesired complexes between the molybdenum atom andoxidized species of the organic agent. The presence of the reducingagent inhibits the organic agent molecules from oxidizing one anotherand rapidly reduces the molybdenum atoms. By quickly reducing themolybdenum atoms and inhibiting the undesired oxidation of the organicagent molecules, the catalyst precursors of the present invention areless likely to form complexes between molybdenum atoms and undesiredoxidized organic agent species, which can reduce performance of thecatalyst precursor in the heavy oil.

Reducing the oxidation state of the molybdenum atoms to less than 4+also increases the percentage of molybdenum in the catalyst precursor ascompared to existing oil soluble molybdenum salts, which typically havean oxidation state equal to or greater than 4+. The inventors have foundthat molybdenum bound to only three organic anions can remainsufficiently soluble in heavy oil while increasing the weight percent ofmolybdenum. Increasing the percentage of molybdenum in the catalystprecursor can significantly reduce the cost of the catalyst precursor.

It is believed that the reducing agent can be helpful in reducing theamount of molybdenum oxides remaining in the final product and/or toreduce the amount of water bound to the molybdenum atoms and/ormolybdenum salts. Hydrogen can be particularly effective at removingmolybdenum oxides and/or water bound to the molybdenum salts. Catalystprecursors manufactured in the presence of hydrogen and/or organicreducing agents under the reaction conditions described herein have beenfound to have particularly good solubility and dispersion inhydrocarbons. It is believed that this increased solubility overexisting catalyst precursors is due in part to the elimination ofmolybdenum oxides and/or to removal of bound water and/or undesiredmolybdenum complexes. However, the invention is not limited to thesefeatures of the invention.

The present invention also includes methods for making the molybdenumcatalyst precursors. The methods of making the catalyst precursorsgenerally include (1) providing a plurality of molybdenum atoms; (2)providing an organic agent comprising a plurality of organic molecules,preferably having between 2 and 14 carbon atoms; and (3) reacting theplurality of molybdenum atoms with the organic agent at a temperaturegreater than about 100° C. and in the presence of a reducing agent. Thereaction yields a molybdenum salt wherein the molybdenum atoms have anaverage oxidation state of less than 4+, preferably less than about3.8+, and more preferably less than about 3.5+.

The organic agent can be any C₂ to C₁₄ hydrocarbon that can react withmolybdenum and form an anion. Examples of suitable organic agentsinclude, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid,octanoic acid, decanoic acid, 2-ethyl butanoic acid, 2-methyl pentanoicacid, 2-ethyl hexanoic acid, and the like.

The hydroprocessing catalyst can be used in various kinds of reactorsand hydrocracking processes to upgrade heavy oil. The hydroprocessingcatalyst of the present invention can more effectively processasphaltene molecules, reduce or eliminate the formation of cokeprecursors and sediment, reduce equipment fouling, and/or increaseconversion rates as compared to conventional hydroprocessing catalysts.

These and other benefits of the present invention will become more fullyapparent from the following description and appended claims as set forthhereinafter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Introduction andDefinitions

The present invention relates to hydrocarbon-soluble molybdenum catalystprecursors that can form a hydroprocessing molybdenum sulfide catalystin heavy oil feedstocks and methods of making the catalyst precursor.The catalyst precursor includes a plurality of cationic molybdenum atomsbonded to a plurality of anionic organic molecules. In a preferredembodiment, at least a portion of the molybdenum atoms are in the 3+oxidation state to give the plurality of catalyst atoms an averageoxidation state of less than 4+, preferably less than about 3.8+, morepreferably less than about 3.5+. The oil soluble molybdenum salts of thepresent invention are manufactured in the presence of a reducing agentto obtain the molybdenum atoms in the desired oxidation state. In apreferred embodiment, the reducing agent is hydrogen or an organicreducing agent.

The terms “colloidal catalyst” and “colloidally-dispersed catalyst”shall refer to catalyst particles having a particle size that iscolloidal in size, e.g., less than about 100 nm in diameter, preferablyless than about 10 nm in diameter, more preferably less than about 5 nmin diameter, and most preferably less than about 3 nm in diameter. Theterm “colloidal catalyst” includes, but is not limited to, molecular ormolecularly-dispersed catalyst compounds.

The terms “molecular catalyst” and “molecularly-dispersed catalyst”shall refer to catalyst compounds that are essentially “dissolved” orcompletely dissociated from other catalyst compounds or molecules in aheavy oil hydrocarbon feedstock, non-volatile liquid fraction, bottomsfraction, resid, or other feedstock or product in which the catalyst maybe found. It shall also refer to very small catalyst particles that onlycontain a few catalyst molecules joined together (e.g., 15 molecules orless).

The term “blended feedstock composition” shall refer to a heavy oilfeedstock into which an oil soluble catalyst precursor composition hasbeen combined and mixed sufficiently so that, upon decomposition of thecatalyst precursor and formation of the catalyst, the catalyst willcomprise a colloidal or molecular catalyst dispersed within thefeedstock.

The term “heavy oil feedstock” shall refer to heavy crude, oil sandsbitumen, bottom of the barrel and resid left over from refineryprocesses (e.g., visbreaker bottoms), and any other lower qualitymaterial that contains a substantial quantity of high boilinghydrocarbon fractions (e.g., that boil at or above 343° C. (650° F.),more particularly at or above about 524° C. (975° F.)), and/or thatinclude a significant quantity of asphaltenes that can deactivate asolid supported catalyst and/or cause or result in the formation of cokeprecursors and sediment. Examples of heavy oil feedstocks include, butare not limited to, Lloydminster heavy oil, Cold Lake bitumen, Athabascabitumen, atmospheric tower bottoms, vacuum tower bottoms, residuum (or“resid”), resid pitch, vacuum residue, and nonvolatile liquid fractionsthat remain after subjecting crude oil, bitumen from tar sands,liquefied coal, or coal tar feedstocks to distillation, hot separation,and the like and that contains higher boiling fractions and/orasphaltenes.

II. Components Used to Manufacture the Catalyst Precursors

The manufacture of the catalyst precursors of the present inventiontypically involves reacting a plurality of molybdenum atoms with aplurality of organic agent molecules in the presence of a reducingagent. If needed, the reaction can be carried out in a solvent.

A. Transition Metal Atoms

The primary metal component of the oil catalyst precursors ismolybdenum. The molybdenum atoms are provided as a molybdenum compoundthat is capable of reacting with an organic agent (e.g., a carboxylicacid such as 2-ethyl hexanoic acid) to form a molybdenum salt. Suitablemolybdenum compounds include molybdenum halides such as molybdenumhexafluoride and molybdenum pentachloride, the various oxides ofmolybdenum such as molybdenum dioxide, trioxide and sesquioxide, and thelike; alkali and alkali earth molybdates such as cesium molybdate,sodium molybdate, potassium molybdate, calcium molybdate and the like;and ammonium molybdate or molybdic acid. In the preferred embodiment ofthis invention, molybdic acid is used.

Other metals can also be included in the catalyst precursors of thepresent invention. Suitable additional metals include transition metalsother than molybdenum. The transition metal can be included in thereaction with the organic agents and/or blended with the molybdenumsalts after manufacture. A preferred additional metal is cobalt.

B. Organic Agent Molecules

The organic agent is one or more oil-soluble organic compounds eachhaving between 2 and 14 carbon atoms and a functional group suitable forreacting with a transition metal to form the anion of an oil solubletransition metal salt (e.g., a molybdenum salt). In a preferredembodiment, the organic agent is a carboxylic acid. Suitable carboxylicacids include aliphatic acids, alicyclic acids, aromatic acids, andphosphor-containing acids. Suitable aliphatic acids include butanoicacid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid,decanoic acid, carboxylic acids with side chains located at the α, β, orγ positions (e.g., 2-ethyl butanoic acid, 2-methyl pentanoic acid,2-ethyl hexanoic acid), and the like. Alicyclic acids includecyclohexanoic, cyclododecanoic and the like. Aromatic acid may containone or two fused rings and contain from 7 to 14 carbon atoms where thecarboxyl group may or may not be attached to the ring, such as benzoic,1 or 2 naphthoic, o-, m-, p-toluic, phenylacetic, 1 or 2 naphthaleneacetic, phenylbutyric acid and the like. Phosphor-containing organiccompounds include 2-ethylhexyl phosphate, and the like. Aliphatic acidsare preferred and 2-ethyl hexanoic acid is particularly preferred forits solubility in heavy oil and its relatively low cost.

Those skilled in the art will recognize that the organic agent moleculescan be modified during the reaction with the molybdenum atoms. Forexample, in the reaction of a carboxylic acid with molybdenum theorganic agent molecules can lose hydrogen to become a carboxylate anion.

In some cases, the organic agent can function as a solvent for thereaction. This is typically the case where the organic agent is a liquidunder the reaction conditions (e.g., 2-ethyl hexanoic acid). However, ifneeded, other solvents can be used. The additional solvent shoulddissolve the organic agent and the molybdenum atoms and not interferewith the reaction between them. Suitable solvents include decant oil,liquid paraffin wax, benzene, toluene, xylene, naphtha, mineral oil,mineral spirits, combinations thereof, and the like.

C. Reducing Agents

The reducing agent is added to the reaction mixture to reduce the metalatoms to more readily form the metal salts and/or to obtain metal saltswith a desired weight percent of metal in the catalyst precursor. In apreferred embodiment, a strong reducing agent is used to reduce and/ormaintain at least a portion of the molybdenum atoms in an oxidationstate below 4+. The average oxidation state of the molybdenum atoms ispreferably less than about 3.8+, more preferably less than about 3.5+.

Any reducing agent that can reduce molybdenum to a 3+ oxidation stateunder the reaction conditions described below can be used with thepresent invention. The reducing agent is preferably hydrogen or anorganic reducing agent. Suitable reducing agents include methane,ethane, olefins such as ethylene and propylene, aldehydes such asformaldehyde, and hydrogen. Hydrogen gas is a particularly preferredreducing agent because of its effectiveness and cost.

The suitability of the reducing agent often depends on the temperatureat which the reaction is performed. At higher temperatures (e.g., 155°C.), organic reducing agents such as methane and formaldehyde havesuitable reducing potential. However, at low temperatures (e.g., below50° C.) or room temperature it can be advantageous to use a strongerreducing agent such as hydrogen gas.

III. Methods of Making Hydroprocessing Catalyst Precursors

The process for making hydroprocessing catalyst precursors according tothe present invention comprises the direct reaction of a pluralitymolybdenum atoms with a plurality of organic agent molecules to form ahydrocarbon-soluble molybdenum salt. The reaction can be carried outwith a molar ratio of molybdenum atoms to organic agent molecules ofless than about 1:20, more preferably less than 1:4, even morepreferably less than about 1:3.8, and most preferably less than about1:3.5.

The reaction of the molybdenum atoms and the organic agent molecules isalso carried out in the presence of a reducing agent. The reducing agentlowers the positive oxidation state of the molybdenum atoms. Themolybdenum atoms, which are typically provided as a molybdenum oxide,are preferably reduced such that substantially no molybdenum oxideremains. By eliminating substantially all molybdenum oxides, thehydrocarbon-soluble molybdenum salts have improved solubility incomparison to commercially available hydrocarbon-soluble molybdenumsalts.

In a preferred embodiment, the reducing agent and reaction conditionsallow for the molybdenum to be reduced to a 3+ oxidation state. Thereaction is carried out in a way that achieves a hydrocarbon-solublemolybdenum salt that has molybdenum atoms with an average oxidationstate of less than 4+. In one embodiment, molybdenum salts with anaverage oxidation state of less than 4+ is achieved by reacting themolybdenum compound and the organic agent molecules in a molar ratio ofmolybdenum atoms to organic agent molecules of less than 1:4, preferablyless than about 1:3.8, and more preferably less than about 1:3.5. Thereducing agent is included in the reaction mixture in an amountsufficient to reduce and maintain at least a portion of the molybdenumatoms in a +3 oxidation state.

The combination of a molar ratio of organic agent molecules of less than1:4 and a reducing environment allows for the formation of catalystprecursors having molybdenum atoms in an oxidation state of less than4+. In a preferred embodiment, the reducing agent is hydrogen gas, whichis passed through or by the reaction mixture to produce the reducingenvironment. Catalyst precursors having molybdenum atoms with an averageoxidation state of less than 4+, preferably less than about 3.8+, morepreferably less than about 3.5+, tend to have improved solubility inheavy oil, which improves the in situ formation of the molybdenumsulfide catalyst. In addition, catalyst with a lower oxidation state canhave fewer organic agent molecules per molybdenum atom, therebyincreasing the molybdenum concentration and reducing cost.

The reaction is preferably carried out at elevated temperatures. Atelevated temperatures (e.g., above 100° C.), the solubility of themolybdenum compounds increases and a more complete reaction with theorganic agent can be achieved. However, the reaction temperature ispreferably maintained below about 300° C. to prevent the molybdenumsalts from decomposing. In a preferred embodiment, the reaction iscarried out at a temperature of from about 100° C. to about 350° C.,more preferably between about 120° C. to about 280° C., and mostpreferably between about 150° C. to about 260° C. It is to be understoodthat among other factors, the temperature and duration of the reactionwill depend upon the particular molybdenum compound and/or theparticular organic agent used. The reaction is carried out for asufficient length of time to allow for substantial reaction to takeplace, which is typically between about 2 hours and about 48 hours ormore.

Maintaining a reducing environment during the reaction can beparticularly advantageous because it causes the reaction between themolybdenum and the organic agent to occur more quickly. In addition, thepresence of the reducing agent reduces the opportunity for the organicagent molecules to oxidize one another, which could otherwise result inthe formation of undesired molybdenum complexes. The presence of thereducing agent during the reaction also helps stabilize the molybdenumatoms in the 3+ oxidation state, which is an oxidation state that isinherently less stable than other oxidation states, such as 4+.

Water is removed from the reaction mixture to obtain a reaction productthat is soluble in heavy oil and to ensure that the molybdenum reactionproceeds. The water can be removed using any technique or combination oftechniques. In a preferred embodiment, the reaction is carried out underconditions that exceed the boiling point of water such that water isremoved as it is formed during the reaction. The water is allowed toescape from the reaction vessel as water vapor. Where hydrogen and/oranother gas is being contacted with the reaction mixture, the water canescape with the gas. If desired, the gas and water vapor can be passedthrough a condenser to remove the water. Optionally, the gas can then berecycled through the reaction mixture.

It is believed that the reducing agent can be helpful to reduce theamount of water bound or complexed to the molybdenum atoms of themolybdenum salt and/or to reduce molybdenum oxide species. Catalystprecursors manufactured in the presence of hydrogen have been found tohave particularly good solubility and dispersion in hydrocarbons. It isbelieved that this increased solubility over existing catalystprecursors is due in part to the removal of bound water and/ormolybdenum oxide species that are not easily removed by heating. It isalso believed to be advantageous to remove molybdenum oxides and/orbound water during the reaction and/or at elevated temperatures and/orin a reducing environment.

If needed, chemical drying agents can be employed to remove water fromthe reaction product, although this is usually not necessary. Any knowndrying technique can be used. For example, water may be removed by theuse of dehydrating agents such as calcium chloride or an azeotropicagent. Those skilled in the art are familiar with dehydrating agents andazeotropic agents.

IV. Catalyst Precursor Compositions Containing Molybdenum

The oil soluble catalyst precursors of the present invention comprise ahydrocarbon-soluble molybdenum salt. The molybdenum salt includes aplurality of cationic molybdenum atoms and a plurality of organicanions, each anion preferably having between 2 and 14 carbon atoms. In apreferred embodiment, at least a portion of the molybdenum atoms arebonded with 3 organic anions and have an oxidation state of 3+ such thatthe plurality of molybdenum atoms have an average oxidation state ofless than 4+, preferably less than about 3.8+, more preferably less thanabout 3.5+.

The percent molybdenum in the molybdenum salt is directly dependent onthe number of organic anions bound to it and the molecular weight of theorganic anions. As the number and weight of the organic anion increases,the weight percent of molybdenum decreases. As mentioned above, higherweight percent molybdenum is desired, so long as the catalyst precursoris soluble in hydrocarbons such as heavy oil. The inventors of thepresent invention have found that the number of organic anions permolybdenum atom can be reduced to 3 while still maintaining sufficientsolubility in hydrocarbons such as heavy oil.

The reduced number of organic anions for at least a portion of themolybdenum salts of the present invention results in a catalystprecursor with an increase in weight percent of molybdenum. For example,where the organic anion is 2-ethyl hexanoate, a catalyst precursorhaving molybdenum atoms with an average oxidation of between 3 and 4will have a weight percent between 19% and 14%. Thus, the weight percentof molybdenum can be increased without adversely affecting solubility byreducing the oxidation state of the molybdenum and consequently thenumber of organic anions bonded thereto.

V. Hydrocarbons Blended with Catalyst Precursors and HydroprocessingCatalysts Formed Therefrom

The catalyst precursors of the present invention can be included in aheavy oil feedstock to form a blended catalyst precursor. The catalystprecursors are designed to remain stable in a hydrocarbon up to adesired temperature. At an elevated temperature, the catalyst precursorsdecompose and react with sulfur in the heavy oil to form a molybdenumsulfide hydroprocessing catalyst.

The oil soluble catalyst precursors preferably have a decompositiontemperature in a range from about 100° C. (212° F.) to about 350° C.(662° F.), more preferably in a range of about 150° C. (302° F.) toabout 300° C. (572° F.), and most preferably in a range of about 175° C.(347° F.) to about 250° C. (482° F.). These preferred decompositiontemperatures allow the catalyst precursor to be thoroughly mixed in ahydrocarbon (e.g., heavy oil) before decomposition occurs.

The catalyst precursor compositions can also be mixed with a diluent toform a mixture with a desirable concentration of molybdenum salt.Examples of suitable hydrocarbon diluents include, but are not limitedto, vacuum gas oil (which typically has a boiling range of 360-524° C.),decant oil (which typically has a boiling range of 360-550° C.), andlight gas oil (which typically has a boiling range of 200-360° C.).

The weight ratio of catalyst precursor composition to hydrocarbon oildiluent is preferably in a range of about 1:1000 to about 1:1, morepreferably in a range of about 1:100 to about 1:1, and most preferablyin a range of about 1:30 to about 1:1 (e.g., 1:20, 1:5 or 1:3).

The catalyst precursor composition can also be pre-mixed with a diluentprior to mixing the precursor with the heavy oil feedstock. The catalystprecursor composition is advantageously mixed with the hydrocarbondiluent at a temperature below which a significant portion of thecatalyst precursor composition starts to decompose, preferably attemperatures in a range of about 25° C. to about 250° C., morepreferably in a range of about 50° C. to about 200° C., and mostpreferably in a range of about 75° C. to about 150° C., to form thediluted precursor mixture. It will be appreciated that the actualtemperature at which the diluted precursor mixture is formed typicallydepends largely on the decomposition temperature of the particularprecursor composition that is utilized. The precursor composition ispreferably mixed with the hydrocarbon oil diluent for a time period in arange of about ½ minute to about 20 minutes, more preferably in a rangeof about ¾ minute to about 10 minutes, and most preferably in a range ofabout 1 minute to about 3 minutes. The actual mixing time is dependent,at least in part, on the temperature (which affects the viscosity of thefluids) and mixing intensity. Mixing intensity is dependent, at least inpart, on the number of mixing stages (e.g., for an in-line staticmixer).

Whereas it is within the scope of the invention to directly blend thecatalyst precursor composition with the heavy oil feedstock, care mustbe taken in such cases to mix the components for a time sufficient tothoroughly blend the precursor composition within the feedstock beforesubstantial decomposition of the precursor composition has occurred. Forexample, U.S. Pat. No. 5,578,197 to Cyr et al. describes a methodwhereby molybdenum 2-ethyl hexanoate was mixed with bitumen vacuum towerresiduum for 24 hours before the resulting mixture was heated in areaction vessel to form the catalyst compound and to effecthydrocracking (see col. 10, lines 4-43). Whereas 24-hour mixing in atesting environment may be entirely acceptable, such long mixing timesmay make certain industrial operations prohibitively expensive.

It has been found that pre-blending the precursor composition with ahydrocarbon diluent prior to blending the diluted precursor mixture withthe heavy oil feedstock greatly aids in thoroughly and intimatelyblending the precursor composition within the feedstock, particularly inthe relatively short period of time required for large-scale industrialoperations to be economically viable. Forming a diluted precursormixture shortens the overall mixing time by (1) reducing or eliminatingdifferences in solubility between the more polar catalyst precursorcomposition and the heavy oil feedstock, (2) reducing or eliminatingdifferences in rheology between the catalyst precursor composition andthe heavy oil feedstock, and/or (3) breaking up the catalyst precursormolecules to form a solute within a hydrocarbon oil diluent that is muchmore easily dispersed within the heavy oil feedstock. It is particularlyadvantageous to first form a diluted precursor mixture in the case wherethe heavy oil feedstock contains water (e.g., condensed water).Otherwise, the greater affinity of the water for the polar catalystprecursor composition can cause localized agglomeration of the precursorcomposition, resulting in poor dispersion and formation of micron-sizedor larger catalyst particles. The hydrocarbon oil diluent is preferablysubstantially water-free (i.e., contains less than about 0.5% water) toprevent the formation of substantial quantities of micron-sized orlarger catalyst particles.

The diluted precursor mixture is then combined with the heavy oilfeedstock and mixed for a time sufficient and in a manner so as todisperse the catalyst precursor composition throughout the feedstock inorder to yield a conditioned feedstock composition in which theprecursor composition is thoroughly mixed within the heavy oilfeedstock. In order to obtain sufficient mixing of the catalystprecursor composition within the heavy oil feedstock so as to yield acolloidal or molecular catalyst upon decomposition of the precursorcomposition, the diluted precursor mixture and heavy oil feedstock arepreferably mixed for a time period in a range of about ½ minute to about20 minutes, more preferably in a range from about 1 minute to about 10minutes, and most preferably in a range of about 2 minutes to about 5minutes. Increasing the vigorousness and/or shearing energy of themixing process generally reduces the time required to effect thoroughmixing.

Examples of a mixing apparatus that can be used to effect thoroughmixing of the catalyst precursor composition and heavy oil feedstockinclude, but are not limited to, high shear mixing such as mixingcreated in a vessel with a propeller or turbine impeller, multiplestatic in-line mixers, or one or more multi-stage centrifugal pumps.According to one embodiment, continuous rather than batch-wise mixingcan be carried out using high energy pumps having multiple chamberswithin which the catalyst precursor composition and heavy oil feedstockare churned and mixed as part of the pumping process itself. Theforegoing mixing apparatus may also be used for the pre-mixing processdiscussed above in which the catalyst precursor composition is mixedwith the hydrocarbon oil diluent to form the catalyst precursor mixture.

In the case of heavy oil feedstocks that are solid or extremely viscousat room temperature, such feedstocks may advantageously be heated inorder to soften them and create a feedstock having sufficiently lowviscosity so as to allow good mixing of the oil soluble catalystprecursor into the feedstock composition. In general, decreasing theviscosity of the heavy oil feedstock will reduce the time required toeffect thorough and intimate mixing of the oil soluble precursorcomposition within the feedstock. However, the feedstock should not beheated to a temperature above which significant decomposition of thecatalyst precursor composition occurs until after thorough and completemixing to form the blended feedstock composition. Prematurelydecomposing the catalyst precursor composition generally results in theformation of micron-sized or larger catalyst particles rather than acolloidal or molecular catalyst. The heavy oil feedstock and dilutedprecursor mixture are preferably mixed and conditioned at a temperaturein a range of about 25° C. to about 350° C., more preferably in a rangeof about 50° C. to about 300° C., and most preferably in a range ofabout 75° C. to about 250° C. to yield the conditioned feedstock.

After the catalyst precursor composition has been well-mixed throughoutthe heavy oil feedstock so as to yield the conditioned feedstockcomposition, this composition is then heated to above the temperaturewhere significant decomposition of the catalyst precursor compositionoccurs in order to liberate the catalyst metal therefrom so as to formthe final active catalyst. According to one embodiment, the metal fromthe precursor composition is believed to first form a metal oxide, whichthen reacts with sulfur liberated from the heavy oil feedstock to yielda metal sulfide compound that is the final active catalyst. In the casewhere the heavy oil feedstock includes sufficient or excess sulfur, thefinal activated catalyst may be formed in situ by heating the heavy oilfeedstock to a temperature sufficient to liberate the sulfur therefrom.In some cases, sulfur may be liberated at the same temperature that theprecursor composition decomposes. In other cases, further heating to ahigher temperature may be required.

If the oil soluble catalyst precursor composition is thoroughly mixedthroughout the heavy oil feedstock, at least a substantial portion ofthe liberated metal ions will be sufficiently sheltered or shielded fromother metal ions so that they can form a molecularly-dispersed catalystupon reacting with sulfur to form the metal sulfide compound. Under somecircumstances, minor agglomeration may occur, yielding colloidal-sizedcatalyst particles. However, it is believed that taking care tothoroughly mix the precursor composition throughout the feedstock willyield individual catalyst molecules rather than colloidal particles.Simply blending, while failing to sufficiently mix, the catalystprecursor composition with the feedstock typically causes formation oflarge agglomerated metal sulfide compounds that are micron-sized orlarger.

In order to form the metal sulfide catalyst, the blended feedstockcomposition is preferably heated to a temperature in a range of about200° C. to about 500° C., more preferably in a range of about 250° C. toabout 450° C., and most preferably in a range of about 300° C. to about400° C. According to one embodiment, the conditioned feedstock is heatedto a temperature that is about 100° C. less than the hydrocrackingtemperature within the hydrocracking reactor. According to oneembodiment, the colloidal or molecular catalyst is formed duringpreheating before the heavy oil feedstock is introduced into thehydrocracking reactor. According to another embodiment, at least aportion of the colloidal or molecular catalyst is formed in situ withinthe hydrocracking reactor itself. Once formed, in some cases, thecolloidal or molecular catalyst can be formed as the heavy oil feedstockis heated to a hydrocracking temperature prior to or after the heavy oilfeedstock is introduced into a hydrocracking reactor. The initialconcentration of the catalyst metal in the colloidal or molecularcatalyst is preferably in a range of about 1 ppm to about 500 ppm byweight of the heavy oil feedstock, more preferably in a range of about 5ppm to about 300 ppm, and most preferably in a range of about 10 ppm toabout 175 ppm. The catalyst may become more concentrated as volatilefractions are removed from the non-volatile resid fraction.

While the highly polar nature of the catalyst compound causes or allowsthe colloidal or the molecular catalyst to associate with asphaltenemolecules, it is the general incompatibility between the highly polarcatalyst compound and the hydrophobic heavy oil feedstock thatnecessitates the aforementioned intimate or thorough mixing of the oilsoluble catalyst precursor composition within the heavy oil feedstockprior to decomposition of the precursor and formation of the colloidalor molecular catalyst. Because metal catalyst compounds are highlypolar, they cannot be effectively dispersed within a heavy oil feedstockin colloidal or molecular form if added directly thereto or as part ofan aqueous solution or an oil and water emulsion such methods inevitablyyield micron-sized or larger catalyst particles.

VI. Examples

The following examples provide exemplary formulas for manufacturingcatalyst precursors according to the present invention. Examples 1, 2, 3and 4 provide formulas for making hydrocarbon molybdenum salts. Inexamples 1, 2, 3 and 4, the molybdenum salts were prepared using acondenser attached to a flask. Condensate was removed by opening avalve. Examples 5, 6, 7, 8 and 9 provide examples of catalyst precursorsdiluted with a hydrocarbon and used for hydrocracking heavy oil.

The composition of used heavy oil in examples 5, 6, 7, 8 and 9 is asfollows. Elemental (w %): Carbon 81.61%, Hydrogen 9.86%, Sulfur 6.27%,Nitrogen 0.68%, Oxygen (calculated) 1.58%. The oil distillation (solidsfree) (w %): IBP-975° F. 21.16%, 975° F.⁺ 78.84%.

Example 1

Example 1 describes a method for making a molybdenum catalyst precursor.4.84 g of molybdic acid (Aldrich, MoO₃≧85.0%) and 12.47 g of2-ethylhexanoic acid (Aldrich, 99%) were mixed together in a flask andthen heated while stirring and purging with 100 ml/min N₂ until thetemperature of the overhead vapor near the liquid was about 185° C. Themixture was held for 1 hour at 185° C. and then purged with 100 ml of amixture of 20% H₂ and 80% N₂ to replace N₂. The mixture was then heldfor 6 hours. The resulting molybdenum catalyst precursor had amolybdenum content of 18 wt %.

Example 2

Example 2 describes a method for making a molybdenum catalyst precursor.4.84 g of molybdic acid (Aldrich, MoO₃≧85.0%) and 13.15 g of heptanoicacid (Aldrich, 96%) were mixed together in a flask and then heated whilestirring and purging with 100 ml/min N₂ until the temperature of theoverhead vapor near the liquid was about 185° C. The mixture was heldfor 1 hour at 185° C. and then purged with 100 ml of a mixture of 20% H₂and 80% N₂ to replace N₂. The mixture was then held for 6 hours. Theresulting molybdenum catalyst precursor had a molybdenum content of 18wt %.

Example 3

Example 3 describes a method of making a molybdenum catalyst precursor.30.0 g of molybdic acid (Aldrich, MoO₃≧85.0%) and 102.2 g of 2-ethylhexanoic acid (Aldrich, 99%) were mixed together in a flask and heatedto 200° C. for 1 hour while stirring and purging with 100 ml/min of N₂.The mixture was then purged with a mixture of 20% H₂ and 80% N₂ and heldat the same temperature for 12 hours. The resulting molybdenum 2-ethylhexanoate contained 14.6 wt % Mo.

Example 4

Example 4 describes a method of making a molybdenum catalyst precursor.18.7 gram of the molybdenum 2-ethyl hexanoate prepared according toExample 3 is mixed with 28.5 grams of 2-ethylhexyl phosphate. Theresulting molybdenum 2-ethyl hexanoate contained 5.9 wt % Mo.

Example 5

Example 5 describes the use of a molybdenum catalyst precursor in ahydrocracking process. A diluted catalyst precursor was prepared bydiluting the catalyst precursor of Example 1 in decant oil to make totalweight 300.0 g. The decant oil and catalyst precursor were heated toabout 80° C. and stirred. The mixture was shaken until it washomogeneous. The sample was then mixed with heavy oil at the weightratio of 2 g/181 g and fed in the Reactor A for hydrocracking.

Example 6

Example 6 describes the use of a molybdenum catalyst precursor in ahydrocracking process. A diluted catalyst precursor was prepared bydiluting the catalyst precursor of Example 2 in decant oil to make totalweight 300.0 g. The decant oil and catalyst precursor were heated toabout 80° C. and stirred. The mixture was shaken until it washomogeneous. The sample was then mixed with heavy oil at the weightratio of 2 g/181 g and fed in the Reactor B for hydrocracking.

Example 7

Example 7 describes the use of a molybdenum catalyst precursor in ahydrocracking process. 18.7 g of the molybdenum 2-ethyl hexanoateprepared according to Example 3 was mixed with 281.3 g of decant oil toproduce a catalyst slurry with 9150 ppm of catalyst. 2 g of thiscatalyst slurry was mixed with 181 g of heavy oil to form the finalfeed, and the mixture was fed in the Reactor A for the hydrocrackingprocess.

Example 8

Example 8 describes the use of a molybdenum catalyst precursor in ahydrocracking process. A diluted catalyst precursor was prepared bydiluting the catalyst precursor of Example 4 in decant oil to make totalweight 300.0 g. The mixture was shaken until it was homogeneous. Thesample was then mixed with heavy oil at the weight ratio of 2 g/181 gand fed in the Reactor B for hydrocracking.

Example 9 Comparison

Example 9 describes the use of a commercially available molybdenumcatalyst precursor in a hydrocracking process. 18.3 g of the comparisonmolybdenum 2-ethyl hexanoate (15.0% Mo) was mixed with 281.7 g of decantoil to produce a catalyst slurry with 9150 ppm of catalyst. 2 g of thecatalyst slurry was mixed with 181 g of heavy oil to form the final feedfor hydrocracking. Catalyst prepared according to Example 9 was fed intoReactors A and Reactor B for comparison purposes.

Reactor Conditions and Results

The hydrocracking reaction for Examples 5 and 7 were carried out inReactor A, while the hydrocracking reaction for Examples 6 and 8 werecarried out in Reactor B. Reaction conditions in Reactors A and B wereidentical with a reaction temperature of 824.5° F., reaction pressure of2200 psig, and a weight ratio of H₂ to feed oil of 19 g/181 g. Thefollowing tables summarize the reaction results:

TABLE A Reaction results in Reactor A Catalyst Sample Comparison Example5 Example 7 Process conversion (w %) 81.3 84.5 84.1 Process HIconversion (w %) 76.6 81.4 84.2 Process Asph conversion (w %) 79.4 83.584.8 C₁-C₃ gas yield 4.91 5.84 7.27 (w %) Bottoms IP-375° F. 1.26 1.420.71 sediment (w %)

TABLE B Reaction results in Reactor B Catalyst Sample Comparison Example6 Example 8 Process conversion (w %) 80.5 83.5 82.8 Process HIconversion (w %) 76.9 80.7 77.8 Process Asph conversion (w %) 80.9 82.681.2 C₁-C₃ gas yield 5.55 5.61 5.81 (w %) Bottoms IP-375° F. 1.71 0.881.72 sediment (w %)

As can be seen from the results, the catalyst for each of Examples 5-8showed improved conversion of hydrocarbons as compared with thecommercially available molybdenum catalyst precursor.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A method of making a molybdenum catalyst precursor for hydrocrackingheavy oil, comprising: providing a plurality of molybdenum atoms;providing an organic agent comprising a plurality of organic moleculeshaving at least one functional group that is reactive with themolybdenum atoms; and reacting the plurality of molybdenum atoms withthe organic agent in the presence of a reducing agent and in a molarratio of molybdenum atoms to organic molecules of less than 1:4 to yieldthe molybdenum catalyst precursor comprised of a molybdenum salt havinga plurality of molybdenum atoms with an average oxidation state of lessthan 4+.
 2. A method as in claim 1, wherein the reducing agent compriseshydrogen or an organic reducing agent or both.
 3. A method as in claim1, wherein the plurality of organic anions comprises anions havingbetween 2 and 14 carbon atoms.
 4. A method as in claim 1, wherein theorganic anion is a carboxylate anion.
 5. A molybdenum catalyst precursoras in claim 4, wherein the carboxylate anions are selected from thegroup consisting of butanoic acid, pentanoic acid, hexanoic acid,heptanoic acid, octanoic acid, decanoic acid, 2-ethyl butanoic acid,2-methyl pentanoic acid, 2-ethyl hexanoic acid, and combinationsthereof.
 6. A method as in claim 1, wherein the weight percentmolybdenum in the molybdenum catalyst precursor is greater than about15.5%.
 7. A method as in claim 1, wherein the percent of molybdenum inthe molybdenum catalyst precursor is greater than about 17%.
 8. A methodas in claim 1, further comprising reacting one or more additional metalsalts comprising a transition metal other than molybdenum with theorganic agent.
 9. A method as in claim 1, further comprising forming adiluted molybdenum catalyst precursor by mixing the molybdenum catalystprecursor with a diluent.
 10. A method as in claim 9, further comprisingforming a blended heavy oil feedstock by mixing the diluted molybdenumcatalyst precursor with a heavy oil feedstock.
 11. A method as in claim1, further comprising forming a blended heavy oil feedstock by mixingthe molybdenum catalyst precursor with a heavy oil feedstock.
 12. Amethod as in claim 1, wherein the reducing agent comprises hydrogen andoptionally an organic reducing agent selected from the group consistingof methane, ethane, olefins, ethylene, propylene, aldehydes andformaldehyde.
 13. A method as in claim 1, wherein the reaction betweenthe plurality of molybdenum atoms and organic agent in the presence ofthe reducing agent is carried out at a temperature above about 100° C.such that water in the reaction product is removed as the reactionproduct is formed.
 14. A method as in claim 1, wherein the reactionbetween the plurality of molybdenum atoms and organic agent in thepresence of the reducing agent is performed at a temperature greaterthan 155° C.
 15. A method as in claim 1, wherein the reaction mixture ispurged with an inert gas prior to reducing with the reducing agent. 16.A method as in claim 1, wherein the average oxidation state of themolybdenum atoms of the molybdenum catalyst precursor is less than about3.8+.
 17. A method as in claim 1, wherein the average oxidation state ofthe molybdenum atoms of the molybdenum catalyst precursor is less thanabout 3.5+.
 18. A method as in claim 1, wherein the molybdenum catalystprecursor forms a molybdenum salt having fewer complexed molecules thatinhibit the molybdenum salt from forming a molybdenum sulfide compoundthan catalyst precursors manufactured without the use of the reducingagent.
 19. A method of making a molybdenum catalyst precursor suitablefor hydrocracking heavy oil, comprising: providing a plurality ofmolybdenum atoms; providing an organic agent comprising a plurality oforganic molecules having at least one functional group that is reactivewith the molybdenum atoms; reacting the plurality of molybdenum atomswith the organic agent in the presence of hydrogen and/or an organicreducing agent selected from the group consisting of methane, ethane,olefins, ethylene, propylene, aldehydes and formaldehyde at atemperature greater than about 90° C. to form a reaction productcomprising a hydrocarbon-soluble molybdenum salt including a pluralityof molybdenum atoms with an average oxidation state of less than 3.8+.20. A method as in claim 19, wherein the organic agent molecules areselected from the group consisting of butanoic acid, pentanoic acid,hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, 2-ethylbutanoic acid, 2-methyl pentanoic acid, 2-ethyl hexanoic acid, andcombinations thereof.
 21. A method as in claim 19, wherein themolybdenum atoms are reacted with the organic agent in the presence ofthe hydrogen and/or the organic reducing agent at a temperature greaterthan about 100° C.
 22. A method as in claim 19, wherein the molybdenumatoms are reacted with the organic agent in the presence of the hydrogenand/or the organic reducing agent at a temperature greater than 155° C.23. A method as in claim 19, wherein the molybdenum catalyst precursorforms a molybdenum salt having higher solubility than a catalystprecursor prepared without the presence of hydrogen.
 24. A method ofmaking a molybdenum catalyst precursor for hydrocracking heavy oil,comprising: providing a plurality of molybdenum atoms; providing anorganic agent comprising a plurality of organic molecules having atleast one functional group that is reactive with the molybdenum atoms;and reacting the plurality of molybdenum atoms with the organic agent inthe presence of hydrogen at a temperature greater than about 100° C. andin a molar ratio of molybdenum atoms to organic molecules of less thanabout 1:3.5 to yield the molybdenum catalyst precursor comprised of amolybdenum salt having a plurality of molybdenum atoms with an averageoxidation state of less than about 3.5.
 25. A method as in claim 1,wherein the molar ratio of molybdenum atoms to organic molecules is lessthan about 1:3.5.